From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:47250 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753080AbcKUKzq (ORCPT ); Mon, 21 Nov 2016 05:55:46 -0500 Subject: Patch "KVM: Disable irq while unregistering user notifier" has been added to the 4.4-stable tree To: ikalvarado@google.com, gregkh@linuxfoundation.org, pbonzini@redhat.com, rkrcmar@redhat.com Cc: , From: Date: Mon, 21 Nov 2016 11:55:56 +0100 Message-ID: <1479725756124127@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled KVM: Disable irq while unregistering user notifier to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-disable-irq-while-unregistering-user-notifier.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 1650b4ebc99da4c137bfbfc531be4a2405f951dd Mon Sep 17 00:00:00 2001 From: Ignacio Alvarado Date: Fri, 4 Nov 2016 12:15:55 -0700 Subject: KVM: Disable irq while unregistering user notifier MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Ignacio Alvarado commit 1650b4ebc99da4c137bfbfc531be4a2405f951dd upstream. Function user_notifier_unregister should be called only once for each registered user notifier. Function kvm_arch_hardware_disable can be executed from an IPI context which could cause a race condition with a VCPU returning to user mode and attempting to unregister the notifier. Signed-off-by: Ignacio Alvarado Fixes: 18863bdd60f8 ("KVM: x86 shared msr infrastructure") Reviewed-by: Paolo Bonzini Signed-off-by: Radim Krčmář Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -199,7 +199,18 @@ static void kvm_on_user_return(struct us struct kvm_shared_msrs *locals = container_of(urn, struct kvm_shared_msrs, urn); struct kvm_shared_msr_values *values; + unsigned long flags; + /* + * Disabling irqs at this point since the following code could be + * interrupted and executed through kvm_arch_hardware_disable() + */ + local_irq_save(flags); + if (locals->registered) { + locals->registered = false; + user_return_notifier_unregister(urn); + } + local_irq_restore(flags); for (slot = 0; slot < shared_msrs_global.nr; ++slot) { values = &locals->values[slot]; if (values->host != values->curr) { @@ -207,8 +218,6 @@ static void kvm_on_user_return(struct us values->curr = values->host; } } - locals->registered = false; - user_return_notifier_unregister(urn); } static void shared_msr_update(unsigned slot, u32 msr) Patches currently in stable-queue which might be from ikalvarado@google.com are queue-4.4/kvm-disable-irq-while-unregistering-user-notifier.patch